MOLDING COMPOUNDS


ah doesn't claim t' be an expeht on dis topic, siss I'be on been doigg it a spell. Mebbe dat gibes me a diffehent pehspeckibe on it dough, duh...uh...? Eff'n yer a noocomeh t' dis process, duuhhhh, yo' kin probab benebit fum some siplificashun, as enny fool kin plainly see.

When yo' plan t' cast in resin, yer facid wid a choice of sebehal manufackures selligg a slew of diffehent producks. Dey doesn't real tell yo' alot bou' how dese producks is diffehent (in a way dat a neophyte kin easy c'prehend), odeh dan probidigg yo' wid alot of technical details.

One digg t' note dat dehe ain't a hard line betweebuhn a moldigg 'n castigg c'poun'. Duh, yo' kin use enny of dese c'poun's f' castigg too... yo' dgest habe t' make sho'nuff dat the, errr, castigg matehial don't stick t' de moldigg matehial, ah reckon. DOIHH! Fry mah hide! It's wise t' cast in a diffehent matehial dan de matehial usid t'make de mold, cuss it all t' tarnation. Duh, yo' kin also git aroun' dis progglem by brushigg on a "barrieh coat", which seals off de matehial, ah reckon. Dis is a necessity when makigg 2-part molds.

SILICONE bs URETHANE RUBBER: Near as ah can tell, dese is de most popular types of moldmakigg matehials usid f' castigg resins. Um uh. ah recommend silicone c'poun's cuz dey is se'f-releasigg (stuff don't stick t' silicone molds ('cept silicone! Huh huh! Fry mah hide!), so yo' doesn't habe t' "grease 'em up" etch & ebehy time-- ) 'n cuz dey're less sensitibe t' moisture. An' room hoomidity = moisture. Um uh. Moisture cuzs li'l tiny buggles t' f'm, 'n propeh sto'age of uredane c'poun's kin be a trimenjus hassle. Dey detehio'ate behy rapid affeh openigg 'n yo' shudd ebacuate the, errr, corntaineh wid an ineht blanketigg gas bef'e sto'age. Don't dat soun' like fun, duh...uh...? Silicone is mo'e expensibe dough. Gawlly! Fry mah hide! Eff'n yer doigg alot of trimenjus molds, duuhhhh, o' castigg corncrete, uh uh uh, den uredane may be rite f' yo'. Lee me lone! Anodeh issue is mix ratios... Dese c'poun's is mixid by webuhite, not boloom. Dehef'e, uh uh uh, yo' need a trible beam scale-- eyeballigg it will not do! Fry mah hide! Doihh, COOL! Fry mah hide! Silicones seem t' come in mo'e exotic mix ratios (like 100:05), but ah's not sho'nuff eff'n dat's a ubehsal truism, dawgone it.

Some exambles of uredane moldigg c'poun's: Synair's Po'-A-Mold line, uh uh uh, includigg Ultra. Some exambles of silicone: Silicones Inc.'s GI-1000 'n Smood-On's Smood-Sil 910. Usual, dey'll tell yo' eff'n it's a silicone c'poun'. I'be lef' out odeh producks, duuhhhh, main cuz ah haben't triid dem, dawgone it.

LATEX may be a fine altehnatibe cuz it's real cheap 'n does a repeckaggle dgob of cappurigg details. It also seems t' habe an incredib long she'f-life. ah usid a kin dat had been opened, uh uh uh uh, used, uh uh uh uh, 'n was mebbe 10 years old (, duh...uh...?); dinnid it wid ammonia 'n ebehydigg seemid hunky-do'y! Fry mah hide! Doihh, COOL! Fry mah hide! De main reasons errrr, whuffo' yo' wuddn't use latex is dat it's time-cornsumigg t' pait it on layeh by layeh wid dryigg time in betweebuhn, as enny fool kin plainly see. Uhhh.... Silicones 'n uredanes doesn't real dry-- dey cure, all obeh, kind of like dgello. So yo' kin git dick-wallid chunks of it fum a siggle pour.

Also, eff'n yer piece is fair large, uh uh uh, yo' habe t' make a suppo'tigg mold outta plasteh. De relatibe din-wallid latex mold will disto't when yo' pour resin into it. Um uh.

PROPERTIES OF COMPOUNDS: Diffehesss betweebuhn the, uhhh, diffehent types of moldigg c'poun's is manifestid in diggs like hardness (mehbshurd in a "Sho'e A" scale-- lowebuhr is sof'eh), mix ratio (part A t' part B, usual by webuhite), pot life (how long yo' habe t' pour it), demold time (when de mold's cured) tear strengd (how much f'ce it takes t' tear the, ERRRR, stuff), elongashun at tear (% it stretches bef'e it tears), 'n biscosity (how dick it is). Dehe is a bunch of odeh mehbshurmins... DOIHH! Fry mah hide!De bendo' 'n spec sheets probide dis inf'mashun, as enny fool kin plainly see. Hehe is some inc'plete exambles:

Produck Sho'e A Mix Ratio Pot Life Demold Tear Strengd
GI-1000 32 100:10 , duh...uh...? , duh...uh...? 120 ppi
Smood-Sil 910 18 100:5 90 min 24 hours 60 ppi

...yabba, yabba, yabba... In prackical tehms, duuhhhh, eff'n yo'be got a piece dat has alot of deep undehcuts, duuhhhh, yer hankerin' a c'poun' dat's fair sof' wid fine elasticity, so yo' kin git the, duh uhh, trappid parts of de mold out. ah dink the, duh uhh, trade-off (in case yo' haben't noticed, uh uh uh uh, dehe's allays a trade-off! Fry mah hide! Doihh, COOL! Fry mah hide!) is de mold's durabiltiby. Anodeh cornsidehashun is de biscosity 'n pot life-- a din mix kin flow into crebices mo'e ready, 'n air buggles kin excape mo'e easy. De longeh it takes f' de mold t' gel, de mo'e time dehe is f' air buggles t' wawk deir way up. It's a fine idea t' bacuum yer mixid c'poun' t' remobe intrainid air buggles, duuhhhh, 'n t'agitate de mold (wid some kind of bibrato'y debice) affeh the, errr, c'poun''s been poured, cuss it all t' tarnation. Duh, yo' kin also brush de pattehn wid an "ipresshun coat" bef'e pourigg, acco'din' t' th' code o' th' heells!

GENERAL ADBICE FOR MOLDING:


Last modified: Saturday, Dganu 6, 2001 6:20 PM